diff --git a/inmail.install b/inmail.install
index 9f6f0c2..bb72393 100644
--- a/inmail.install
+++ b/inmail.install
@@ -34,16 +34,31 @@ function inmail_get_requirements() {
     /** @var \Drupal\inmail\Entity\PluginConfigEntity $entity */
     foreach ($entities as $entity) {
       // Add requirements specific entity and plugin keys.
+      $plugin_id = $entity->getPluginId();
       $entity_key = $plugin_type . '_entity_' . $entity->id();
-      $plugin_key = $plugin_type . '_plugin_' . $entity->getPluginId();
+      $plugin_key = $plugin_type . '_plugin_' . $plugin_id;
+      try {
+        /** @var \Drupal\inmail\PluginRequirementsInterface $plugin */
+        $plugin = $entity->getPluginInstance();
 
-      // Check entity instance requirements.
-      $requirements[$entity_key] = $entity->checkInstanceRequirements();
+        // Check entity instance requirements.
+        $requirements[$entity_key] = $plugin->checkInstanceRequirements();
+        // Add title in case requirements are not empty.
+        if (!empty($requirements[$entity_key])) {
+          $requirements[$entity_key]['title'] = $entity->label() . ' (' . $entity->id() . ')';
+        }
 
-      // Check plugin requirements only if it is not already checked.
-      if (!isset($requirements[$plugin_key])) {
-        $plugin = $entity->getPluginInstance();
-        $requirements[$plugin_key] = $plugin::checkPluginRequirements();
+        // Check plugin requirements only if it is not already checked.
+        if (!isset($requirements[$plugin_key])) {
+          $requirements[$plugin_key] = $plugin::checkPluginRequirements();
+        }
+      }
+      catch (\Drupal\Component\Plugin\Exception\PluginException $e) {
+        $requirements[$plugin_key] = [
+          'title' => t('Missing plugin @id', ['@id' => $plugin_id]),
+          'description' => t('Inmail @type plugin @id is missing and cannot be used.', ['@type' => $plugin_type, '@id' => $plugin_id]),
+          'severity' => REQUIREMENT_ERROR,
+        ];
       }
     }
   }
diff --git a/src/Entity/AnalyzerConfig.php b/src/Entity/AnalyzerConfig.php
index 90e4873..e287449 100644
--- a/src/Entity/AnalyzerConfig.php
+++ b/src/Entity/AnalyzerConfig.php
@@ -43,18 +43,11 @@ namespace Drupal\inmail\Entity;
 class AnalyzerConfig extends PluginConfigEntity {
 
   /**
-   * Constructs a new AnalyzerConfig.
+   * The Inmail plugin type.
    *
-   * @param array $values
-   *   An array of values to set, keyed by property name. If the entity type
-   *   has bundles, the bundle key has to be specified.
-   * @param string $entity_type
-   *   The type of the entity to create.
+   * @var string
    */
-  public function __construct(array $values, $entity_type) {
-    parent::__construct($values, $entity_type);
-    $this->pluginType = 'analyzer';
-  }
+  protected $pluginType = 'analyzer';
 
   /**
    * The weight of the analyzer configuration.
diff --git a/src/Entity/DelivererConfig.php b/src/Entity/DelivererConfig.php
index 0cbed0a..797620c 100644
--- a/src/Entity/DelivererConfig.php
+++ b/src/Entity/DelivererConfig.php
@@ -42,16 +42,10 @@ namespace Drupal\inmail\Entity;
 class DelivererConfig extends PluginConfigEntity {
 
   /**
-   * Constructs a new DelivererConfig.
+   * The Inmail plugin type.
    *
-   * @param array $values
-   *   An array of values to set, keyed by property name. If the entity type
-   *   has bundles, the bundle key has to be specified.
-   * @param string $entity_type
-   *   The type of the entity to create.
+   * @var string
    */
-  public function __construct(array $values, $entity_type) {
-    parent::__construct($values, $entity_type);
-    $this->pluginType = 'deliverer';
-  }
+  protected $pluginType = 'deliverer';
+
 }
diff --git a/src/Entity/HandlerConfig.php b/src/Entity/HandlerConfig.php
index 0344acb..5e97708 100644
--- a/src/Entity/HandlerConfig.php
+++ b/src/Entity/HandlerConfig.php
@@ -42,17 +42,10 @@ class HandlerConfig extends PluginConfigEntity {
   // @todo Implement HandlerConfig::calculateDependencies() https://www.drupal.org/node/2379929
 
   /**
-   * Constructs a new HandlerConfig.
+   * The Inmail plugin type.
    *
-   * @param array $values
-   *   An array of values to set, keyed by property name. If the entity type
-   *   has bundles, the bundle key has to be specified.
-   * @param string $entity_type
-   *   The type of the entity to create.
+   * @var string
    */
-  public function __construct(array $values, $entity_type) {
-    parent::__construct($values, $entity_type);
-    $this->pluginType = 'handler';
-  }
+  protected $pluginType = 'handler';
 
 }
diff --git a/src/Entity/PluginConfigEntity.php b/src/Entity/PluginConfigEntity.php
index 125a6c6..1fe4c63 100644
--- a/src/Entity/PluginConfigEntity.php
+++ b/src/Entity/PluginConfigEntity.php
@@ -3,7 +3,6 @@
 namespace Drupal\inmail\Entity;
 
 use Drupal\Core\Config\Entity\ConfigEntityBase;
-use Drupal\inmail\PluginRequirementsInterface;
 
 /**
  * Defines a config entity skeleton for plugin configuration.
@@ -46,13 +45,6 @@ abstract class PluginConfigEntity extends ConfigEntityBase {
   protected $pluginInstance;
 
   /**
-   * The Inmail plugin type - deliverer, analyzer, handler.
-   *
-   * @var string
-   */
-  protected $pluginType;
-
-  /**
    * Returns the plugin ID.
    *
    * @return string
@@ -90,12 +82,15 @@ abstract class PluginConfigEntity extends ConfigEntityBase {
   /**
    * Returns the plugin instance.
    *
-   * @return \Drupal\inmail\Plugin\inmail\Analyzer\AnalyzerInterface|\Drupal\inmail\Plugin\inmail\Deliverer\DelivererInterface|\Drupal\inmail\Plugin\inmail\Handler\HandlerInterface
-   *   The instantiated plugin.
+   * @return \Drupal\inmail\Plugin\inmail\Analyzer\AnalyzerInterface|\Drupal\inmail\Plugin\inmail\Deliverer\DelivererInterface|\Drupal\inmail\Plugin\inmail\Handler\HandlerInterface The instantiated plugin.
+   * The instantiated plugin.
+   *
+   * @throws \Drupal\Component\Plugin\Exception\PluginException
+   *   Throws an exception in case of missing plugin.
    */
   public function getPluginInstance() {
     if (empty($this->pluginInstance)) {
-      return \Drupal::service('plugin.manager.inmail.' . $this->pluginType)->createInstance($this->plugin, $this->configuration);
+      $this->pluginInstance = \Drupal::service('plugin.manager.inmail.' . $this->pluginType)->createInstance($this->plugin, $this->configuration);
     }
 
     return $this->pluginInstance;
@@ -112,27 +107,6 @@ abstract class PluginConfigEntity extends ConfigEntityBase {
   }
 
   /**
-   * Checks requirements of the current configuration instance.
-   *
-   * @return array
-   *   Returns the structured verbose output if requirements are not met.
-   *   In case of no instance requirements, an empty array is returned.
-   */
-  public function checkInstanceRequirements() {
-    $requirements = [];
-    if ($plugin = $this->getPluginInstance()) {
-      $requirements = $plugin->checkInstanceRequirements();
-    }
-
-    // Add title in case requirements are not empty.
-    if (!empty($requirements)) {
-      $requirements['title'] = $this->label();
-    }
-
-    return $requirements;
-  }
-
-  /**
    * Flag determining whether a plugin is available to be used in processing.
    *
    * @return bool
diff --git a/tests/src/Kernel/ProcessorTest.php b/tests/src/Kernel/ProcessorTest.php
index 6ba43a4..126cc42 100644
--- a/tests/src/Kernel/ProcessorTest.php
+++ b/tests/src/Kernel/ProcessorTest.php
@@ -90,10 +90,9 @@ EOF;
       'severity' => REQUIREMENT_ERROR,
     ], $plugin::checkPluginRequirements());
     $this->assertEquals([
-      'title' => t('Unavailable Analyzer'),
       'description' => t('Wrong instance configuration.'),
       'severity' => REQUIREMENT_ERROR,
-    ], $unavailable_analyzer->checkInstanceRequirements());
+    ], $plugin->checkInstanceRequirements());
     $this->assertEquals(FALSE, $unavailable_analyzer->isAvailable());
     // The body message has not changed. It implies UnavailableAnalyzer
     // did not run.